Ethylene Polymerization and Copolymerization by Palladium and Nickel Catalysts Containing Naphthalene-Bridged Phosphine–Sulfonate Ligands

A series of naphthalene-bridged phosphine–sulfonate ligands and the corresponding Pd(II) complexes [κ 2 ( P, O )-2-(R 2 P)-1-naphthalenesulfonato]Pd(Me)(dmso) ( 1, R = Ph; 2, R = o -MeO-C 6 H 4; 3, R = Cy) and Ni(II) complexes [κ 2 ( P, O )-2-(R 2 P)-1-naphthalenesulfonato]Ni(η 3 -C 3 H 5 ) ( Ni-1, R = o -MeO-C 6 H 4; Ni-2, R = Cy) have been prepared and characterized. The analogous benzo-bridged phosphine–sulfonate Pd(II) complex [κ 2 ( P, O )-(R 2 P)-benzenesulfonato]Pd(Me)(dmso) ( 2 ′, R = o -MeO-C 6 H 4 ) and Ni(II) complex [κ 2 ( P, O )-(R 2 P)-benzenesulfonato]Ni(η 3 -C 3 H 5 ) ( Ni-1 ′, R = o -MeO-C 6 H 4 ) were prepared for comparison. In ethylene polymerization, complex 2 showed activity of up to 7.5 × 10 6 g mol –1 h –1, which is among the most active palladium catalysts for ethylene homopolymerization. Under the same conditions, complex 2 showed up to 1 order of magnitude higher catalytic activity than complex 2 ′, generating polyethylene with slightly smaller molecular weight and similar branching density. The Ni(II) complex Ni-1 was also more active than complex Ni-1 ′, generating polyethylene with up to 1 order of magnitude higher molecular weight. In ethylene–methyl acrylate copolymerization, complex 2 showed lower activity, affording a copolymer with higher methyl acrylate incorporation and higher copolymer molecular weight in comparison to complex 2 ′.